Air circuit breaker



July 7, 1953 Filed Jui# 1, .1948

A. R. MILLER AIR CIRCUIT BREAKER 2 Sheets-Sheet 1 ya Y.

Patented July 7, 1953 AIR CIRCUIT BREAKER Archie R. Miller, Easton, Pa., assignor, by mesne assignments, to Roller-Smithv Corporation, Bethlehem, Pa., a corporation of New Jersey Application July 1, 1948, Serial No. 36,309

` (c1. zoo-147) 2 Claims.

'I'his invention relates toa'ir circuit breakers particularly applicable tothe interruption of alternating currents and furtherprelates to a method and provision of means for extinguishing the arc and for cooling and condensing the vapors and gases.

The invention is based in one respect upon causing the current to induce magnetic fields in adjoining parts and thereby forcing the arc in an upward direction. The invention also comprises the provision of quencher and condenser plates for receiving'the attenuated arc and dissipating it and for cooling and condensing the vapors or gases and thereby avoiding any material discharge of vapors or gases to the outside atmosphere.

A co-pending divisional application hereof, Serial No. 108,150, iiled August 2, 1949. contains claims particularly directed to the provision of the quencher and cooling plates in relation to the arcing region.

One object is to reduce the size of the breaker and the required space for mounting for any given capacity. Owing to the fact that .there y is no appreciable discharge of vapors or gases from the breakers, they may be mounted closely together, especially in stacking one above the other. Also, this freedom from discharge of vapors or gases avoids the necessity of enclosing the breakers within cubicles and thereby eliminates such additional expense and required space therefor.

Another object is to avoid the use and cost of blow-out magnets and the space required by them. Another object is to control the movement of the arc in such a manner that-when the contact surfaces are-separatedthey are relieved from any objectionable ar'cing effects and the space' between them upon separation is cooled and any restriking of the arc is avoided. Another object is to provide a comparatively simple form of structure which may be easily assembled and which will permit convenient accessibility to all parts and permit separate removal of thequencher and condenser plates and access to the parts of the switch between-which the arc is drawn. Other objects and advantages will be understood from the following description and accompanying drawings which illustrate a preferred embodiment `of the invention.

Fig. 1 is a vertical section of the breaker in aV plane perpendicular to the supportingpanel; and Fig. 2 is a front elevation showing the interior of the upperportion of the breaker, the front cover plate being removed.

Fig. 1 shows a form of mechanism for actuating the breaker to closed position andrfor releasing it but as this forms no part of the present invention and as any suitable mechanism may be used, it will be described only generally.

A supporting panel I of insulating material is shown at the left of Fig. 1. A U-shaped frame 2 is fixed to the support and between its two outwardly extending arms is pivotally mounted a square shaft 3. Two upwardly extending side plates 4 are mounted on the shaft 3 and insulated therefrom. These side plates are actuated to the closed position of the breaker shown in Fig. 1 by a toggle mechanism comprising a lever 5 pivotally mounted between the arms of the frame 2. The inner end of the lever 5 is pivotally connected to a link 6 which in turn is pivotally connected to another link 1, the inner end of which is pivotally connected to the side plates 4. Another link 8 is pivotally connected to the connection between the links Ii and 'land has its lower end pivotally connected to a lever 9. This lever is pivoted at its upper end between the arms of the frame 2 and is restrained at its lower end by a latch III pivotally mounted between the arms of the frame. When this latch is tripped automatically by responsive means not shown, the breaker moves to its open position, or it may be opened manually by actuation of the latch shaft.

Mounted between the breaker side plates 4 is a copper block H having an inner contact surface which, when the breaker is closed, engages a main forwardly spring pressed contact element I2 pivotally mounted on and electrically connected to a main conductor or bar I3 passing through and supported on the panel I. A flexible copper conductor I4 is clamped at its upper end to the block II andl secured at its lower inner end to a conducting copper block I5 xed to the panel and in electrical connection with the other main conductor vor bar I6 passing rearwardly through the panel.

The side plates 4 of the breaker are bent toward each other above their middle portions and then, as shown in Fig. 2, extend upward parallel to each other in much closer relationship than the lower portions. Between the upper ends of the side plates is pivotally supported a block Il, as shown in Fig. 1, of cold rolled steel. This supports the movable arc contact element I8 of the breaker. This element is a copper strap, or of other non-magnetic metal, the upper end of which curves around the rounded upper end of the block I'I, then down along its rear face, is then bent at right-angles to pass under the lower end of the block and is then bent again at right-angles to extend downwardly therefrom. It is secured to the block by screws I8a. The contact element I8 is faced on its rear surface by a contact I 8b of suitable arc resisting material such as a composition of silver or copper tungsten, or othersuitable materials. A copper strap I9 is secured and soldered at its upper end to the lower end of the secondary contact aeaaeve When the breaker opens, the main Contact is V- opened rst between the block and the conductor l2 and then the auxiliary contact lb' separates from the xed auxiliary Contact .and

in this movement the block Il and'elernent 'I2 swing rearwardly on their pivotto maintain connection with the secondary xed contact until as having tapered lower edges. On the outside of each of the steel plates 3D is another sheet 33 of insulating-material oyasbestos lumber which extends from Vthiepanel. tothe front `cover plate and from below the steel plates 30 to some dis i tance above them and serve a purpose later eX- plained. They are supported by the upper screw bolts 30a'which also pass through the plates 30,

sheets 3| and the plates 32.

O n 'the inside of the front cover plate 2D and supported thereby by the screw bolts 34a, is a cold y rolled steel plate 34 forming the front plate of the breaker is in a position to transfer the arc" 5' to the arc runners. In closing the breaker, the secondary contacts rst engage and then the main contacts engage. e

`The means for. extinguishing and quenching the arc and for absorbing the vapors and gases are enclosed by the panel at the rearJ a iront cover plate 2li, side cover plates 23d and 29h and a top cover plate these plates being of insuv lating material. The enclosure is open at the bottom,

Referring to l, the main conductor i3 is supported by an angle iron 2| at the back Vof the panel. and one of its bolts 2id extends through the .panel and engages 'a cold rolled steel 'block 22yon the front of the` panel. The stationary secondary contact element is in the form of a copper or of other non-magnetic metal bar or strap 23 having a contact of suitable arc ren sisting metal which faces the movable Contact la. The contact element 233 is inclined rearwardly toward the panel and then extends upwardly to form a runner for the arc. This element is secured to and is backed along most of its length by a supporting bar 24 of hard copper. The lower end of this bar is supported on the main conductor I3 and secured thereto by a screw bolt 24a which also passes rearwardly through the lower end portion of the contact element 23. The bar 24 is backed by a cold rolled steel plate 25 which is secured thereto by screws 25d. In front oi' the lower end ol? the bar 2li and below the lower end of the conducting strip 23 an angular bracket 26 of insulating material is xed to the bar 24 to serve as a shield. f

The inclined front face of the steel block 22 serves to support the back of the steel plate 25. The top of the steel block is covered by a small plate 2l rof insulating material. Above this and secured to the panel by the bolts 28a is a cold rolled steel plate 28. yThis extends upwardly cpposite and near the bach of the'stationary con ducting element orrunner and also some distance beyond its upper end and is labout twice the width of the runner 23, thus extending sidewise beyond both edges of the runner. It is faced by a thin sheet Eil of insulating material such as asbestos lumber.

Secured to opposite sides of the steel back plate 28 by screw bolts 30a are cold rolled steel plates 33. These plates are shown in Fig. l as of rectangular form and extend forwardly at opposite sides or" the arc runner 23. The inside faces of these plates are lined by sheets 3| of insulating material, such as asbestos lumber, and are secured at the rear by the screws 30a. These sheets extend forwardly to the viront cover 23. They are faced on their inside upper portions on opposite sides of the arcing region by insulating plates 32 of asbestos lumber and are held in place by the bolts The two sets of plates 33, 3| and 32 are respectively clamped together by additional bolts 32a. These plates 32 are shown in Fig. 2

, rear steel plate 28.

the arcin'g region and of the same size as the The inner face of the plate 34 is lined with a sheet .35 of insulating asbestos lumber. A strap 36 of hard copper bent at rightangles is mounted on the inside `of the sheet 35. the bolts'llc servingto hold it in place. The lower leg 4of the strapSi extends rearwardly. A strap 3l of hard copper'or other non-magnetic metal is xed by screws 3la to the lower sideof the strap 35. The strap 3'? extends rearwardly toward and just above'the pathof movement of the conductor lil of the breaker and then turns and extends forwardly and upwardly at an ang-le of about 45 'to fo'rrn the front'arc runner. The otherv portion of the strap 3l' extends forwardly through an opening in 4the insulating sheet 35 and through an opening 34hv inthe steel plate 34 and through a similar opening in the front cover 253, and then is bent at right-angles ltoextend downwardly some distance in front of the breaker. A detachable flexible lead 31h extends from the lower end of 3l and is-in electrical connection `with conductor i4 and clamped inplace by the clamping block Ma. On the under side of the inclined portion of the strap 3l is secured by the screw a cold rolled steel'bar or plate 38 of considerable thickness. l

` A cold rolled steel plate 3S! is secured by screws te eachvertically' extending end of 'the plate 34 and extends rearwardly about half-way of the breaker to embrace the arcing'region. The inner edge of these plates is inclined as shown in Fig. l; and these plates are interposed between and covered on their opposite sides by the insulating sheets 3| and 33-already described. They are clamped together by additional bolts 33a. A rectangular plate '48 of insulating material extends across the top of the plate 34' and sheet 35, as shown in Fig. l.

The form of structure of the cooling and condensing plates and their relationship to other parts will now be described. The side plates 33 extend above'the arcing region and have a series of upwardly extending teeth 33h extending along their upper edges `'and serve as positioning and spacingV means for the cooling and condensing plates 4|. These plates are of hard copper and have a large' surface area occupying the VJfull width of the upper portion of the casing and considerably beyond the Awidth ofthe arcing region and have downwardly extending leg portions '4Ib within-the space between 'the side covers 20d and 2Gb and the insulating sheets 33. The'vapors and gases resulting vfromv the arci'ng thus have a path from'the arcingregion up between the plates 4| then sidewise and then down in two paths through the spaces between the legs 4|b. The plates 4| are'held in spaced position at their upper end corners by bars 42 of insulating material. These bars are notched on their lower sides to engage and space the plates. The bars are supported from the 'top cover 20c by the screws 42a and are also engaged by certain upper screws of the side cover plates and of the front cover plate. A support plate 43 of insulating material for the rear end of the top cover is secured to the panel by the bolts 43a and is engaged by the screws 43h which pass through the top cover. It is also engaged by the screws 43C passing through the side covers. Spacing strips 44 of insulating material are introduced between the top portions of the insulating sheets 3l and 23 and extend from the front cover to the panel. The lower front corners of these strips are notched to rest on the insulating strip 4U. The rear ends of the strips p-ass through slots in the lower portion of the rear plate 43 and rest on top of the lower rear plate 28. At the lower front corners of the side cover plates are corner blocks of fibre engaged by screws which fasten the lower corners of the front cover and side covers together.

In opening the breaker and when the arc is drawn between the arcing contact surfaces liib and 23a as already described, the top portion of the conducting element I8 has then passed close to the inner end of the arc runner 3'l. In the meantime the alternating current has induced magnetic fields in the sheet steel enveloping plates 25, 28 and 30 and in the steel block I1 which drives the arc upwardly and along the arc runners 23 and I 8. As the arc lengthens it is forced upwardly and transferred to between the arc runners 23 and 31. The current then continues to induce magnetic fields in the embracing plates 28 and 30 and also induces currents in the embracing plate 34 and side plates 39 and in the plate 38, the current passing around the latter plate to the shunt connection 3'! and thence to the conductor I4. The structure as disclosed permits the travel of the arc to be fast enough to avoid excessive heating or melting of the conducting parts and slow enough to permit the current to approach its zero value in its current cycle by the time it has reached the upper ends of the arc runners and thereby accomplish the extinguishment of the arc within the enclosed arcing space. This space embracing the arc by the iron or steel plates cannot be too wide as the induced magnetic fields would be too weak to effectively react on the arc to drive it upwardly; also it is desirable to have the side walls close enough to aid in extinguishment by their cooling effect.

The cooling and condensing plates 4I are close to the top of the arcing region and afford a much wider path than that of the arcing region. This permits the heated gases and vapors to pass from the arcing region to within the spaces between the condensing plates where they are cooled and condensed. Also the vapors and gases are afforded a long length of travel between these plates upwardly and then downwardly between their depending legs. The vapors and gases are thereby effectively cooled and condensed, with the result that there is no material discharge thereof from the bottom opening of the enclosures.

Convenient accessibility to the interior of the breaker is afforded by permitting the enclosing casing and parts carried thereby and the cooling and condensing plates to be removed as a unit. This is accomplished by removing the -bolts 28a and 43a from the back of the panel which then allows the unit to be raised from the other parts 0f the breaker. The unit may then be readily inspected and further dismantled if necessary. Likewise the movable parts of the breaker and stationary contact parts are fully exposed for inspection upon the removal of the unit. If desired the enclosing casing may be made separately removable from the cooling and condensing plates.

It is thus apparent that this improvement has various important advantages such as simplicity of structure, compactness and small size, effective extinguishment of the arc, cooling and condensing of the vapors and gases with no outward appreciable discharge thereof and durability under long continued use. It also permits the stacking of the breakers in close proximity to each other sidewise as well as one above the other; and that, together with their small size, reduces the space required in their switchgear assemblies.

A single pole breaker has been described for simplicity but it is apparent that the improvement may be applied to any number of poles adapted for simultaneous operation or control.

Although a particular embodiment of the invention has been shown and described, it will be understood that it is subject to various modications according to particular requirements and to the preference of the designer without departing from the scope of the invention.

I claim:

1. An air circuit breaker comprising a movable element for opening and closing the breaker, a xed arcing contact part and a movable arcing contact part of non-magnetic metal, a backing of magnetic material on said movable arcing part whereby a magnetic field is induced for directing the movement of the arc, said backing of magnetic material being pivotally mounted on said movable element, and a spring for biasing said backing of magnetic material and said movable arcing contact part towards said fixed arcing contact part for maintaining contact between said parts during a portion of the opening movement of the breaker.

2. An air circuit breaker comprising a movable element for opening and closing the breaker, a fixed arcing contact part and a movable arcing contact part of non-magnetic metal, a backing of magnetic material on both of said parts whereby magnetic fields are induced for directing the movement of the arc, said backing of magnetic material on said movable arcing part being pivotally mounted on said movable-element, and a spring for biasing said last named backing of magnetic material and said movable arcing contact part towards said xed arcing contact part for maintaining contact between said parts during a portion of the opening movement of the breaker.

ARCI-IIE R. MILLER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,313,176 Evans Aug. 12, 1919 1,811,451 VAustin June 23, 1931 2,334,562 Latta Nov. 16, 1943 2,337,949 Walle Dec. 28, 1943 2,340,682 Powell Feb. 1, 1944 2,408,352 Titus Sept. 24, 1946 2,416,164 Ellis Feb, 18, 1947 2,417,683 Harlow Mar. 18, 1947 2,446,027 Scott July 27, 1948 2,446,859 Traver Aug. 10, 1948 2,538,370 Lerstrup Jan. 16, 1951 

